Factors associated with physical inactivity among the pre‐school children: A cohort of 1681 participants

To investigate the risk factors associated with physical inactivity of young children in Hong Kong.

1 Physical inactivity is a common problem among Hong Kong children, as they are influenced by parents' behaviour and attitudes towards physical activity, their socio-economic status, gender, and the use of time on digital devices. 2 There is a lack of a comprehensive and updated study contributing to investigating associated risk factors in pre-school children's physical inactivity in Hong Kong.

What this paper adds
1 Children's physical activity level was mainly determined by the behaviour and support from their parents.Also, we suggest that family-based physical activities could be promoted by the implementation of public health policy to increase the young children's tendency in physical activity.

Physical inactivity is a common problem among children in Hong
Kong.According to Active Healthy Kids Hong Kong, 63.7% of children aged 6 to 13 (mean age: 8.7) had less than 1 h of moderate-to vigorous-intensity physical activity (MVPA) each day. 1 The World Health Organization has stated that regular physical activity can prevent and control noncommunicable diseases, such as heart disease, stroke, diabetes and even malignancies. 2Also, physical inactivity is directly linked to the risk of obesity and other health problems in children. 3 Previous research has found that high levels of physical inactivity among children are associated with the female sex, lower socio-economic status, having physically inactive parents 4 and excessive screen time. 5These findings suggested that parents played an essential role in determining the physical activity level of pre-school children.Parental support behaviours and a positive attitude towards physical activity of parents, as well as the parents' perceptions on their children's competence were identified as the significant factors. 6lthough prior studies have examined the factors contributing to child physical inactivity, many of these studies were conducted a decade ago 7 or focused on a single country. 4Additionally, there is a lack of related studies that has been conducted in the context of China or East Asia. 8Some studies were limited to the analysis of older children instead of younger children, 9 despite the distinct contributing factors of physical between these two groups.In view of that, the present study aims to investigate the risk factors associated with physical inactivity among children attending preschools in Hong Kong.It is hypothesised that the child's physical health, the parent's physical activity level, and the child's electronic gaming time have an impact on the child's physical inactivity.

Subject recruitment
The current study is based on data from a follow-up study that was conducted in 2016-2017 as part of a prospective cohort study named Studying Impact of Nutrition on Growth (SING) started in 2015.Cluster sampling was used by treating each kindergarten or nursery as one cluster.First, a full list of kindergartens and nurseries was obtained from the Education Bureau of the Hong Kong SAR Government for the academic year of 2014-2015.Then, the kindergartens and nurseries were divided into 18 districts of Hong Kong, and random numbers were generated to select the schools.For each selected school, the school principal was contained to obtain consent for study participation.The parents of students from the chosen schools were invited to participate, and written consent was also obtained from them.

Survey instruments
The survey has been pilot tested and validated by a team of experts consisting of physicians, epidemiologists and health-care professionals. 10The surveys included a total of 10 questions.Parents were asked to provide information on (i) socio-economic background: sex of the child, ages of the child and parents, order of birth of the child, occupational status and educational background of parents; (ii) health-related factors: gestation at time of birth, and the number of times of the child had been hospitalised since birth; (iii) types of leisure activities: the amount of time the child spent on electronic games in the past 7 days, and the physical activity level of the child and the care giver during weekends and weekdays.

Definition of variables
In this study, respondents were asked about the amount of time their children spent on leisure activities, including physical activity and electronic games, on a daily basis.Their responses were then categorised into 'less than one hour' and 'at least one hour' per day.'Less than one hour' was defined as physical inactivity for children based on World Health Organization's recommendation of at least 60 min of MVPA for children aged between 3 and 17. 11 The cutoff of less than 1 h/day for electronic games was set by the American Academy of Paediatrics. 12In terms of care givers, their level of physical activity was classified into 'no physical activity' and 'some physical activity'.'No physical activity' was defined as care givers who did not engage in any moderate to vigorous physical activity and was therefore considered as physical inactive.'Some physical activity' referred to care givers who engaged in at least 15 min of physical activity.

Statistical analysis
The database was imported into and analysed using IBM Statistical Package for Social Sciences (SPSS) software version 26.0 (Chicago, USA). 13The first part of the analysis was a descriptive summary of the study participants, which displayed the proportion of participants by various characteristics and their mean age with standard deviation.The second part was a multiple logistic regression analysis that examined the association between the explanatory factor and the outcome variables (physical inactivity) after adjusting for confounding variables.All variables were entered simultaneously in the model.The prevalence of the outcome variable by various characteristics among participants was also evaluated.All P value less than 0.05 was regarded as statistically significant.

Ethics approval
The study was approved by the Clinical Research Ethics Committee (CREC), Chinese University of Hong Kong (CUHK) and New Territories East Cluster (NTEC) (CREC-2013-632).Our results will be disseminated through media outlets and presentations at scientific conferences and academic events.

Participant characteristics
A total of 1681 responses were collected.The children had a mean age of 5.78 (SD = 0.64) at follow-up.Over half of them were males (n = 898, 53.4%), delivered at 37-39 weeks of gestation (n = 838, 57.7%), the firstborn of the family (n = 969, 66.6%) and hospitalised less than three times since birth (n = 686, 61.9%).The mean ages of the father and the mother when they joined the study were 36.06 (SD = 6.22) and 32.71 (SD = 4.53), respectively.A total of 93.9% of the fathers (n = 1331) and 50.3% of the mothers (n = 727) were working full-time, and nearly half of them had post-secondary education (fathers: n = 716, 50.1%; mothers: n = 713, 49.5%).A total of 17.3% of the children spent more than 1 h on electronic games (n = 194).More than 70% of the children spent less than 1 h on physical activity on weekdays (n = 1201, 71.4%), and one-quarter of them spent less than 1 h on physical activity on weekends.As far as the physical activity level of the care givers is concerned, 58.0% (n = 964) and 56.7% (n = 936) reported doing no physical activity at all during weekdays and weekends, respectively (Table 1).

Prevalence of outcome
A higher prevalence of physical inactivity during weekdays was found among children who were females (73.9%, vs. 69.3%for males), whose gestational age at delivery was 37-39 weeks (73.3%, vs. 71.0%for 40 weeks or more, and 67.8% for 36 weeks or less), thirdborns of the family (80.0%, vs. 77.0%for secondborns, and 69.6% for firstborns), had been hospitalised three times or more since birth (75.7%, vs. 67.8%),and spent less than 1 h/day on electronic games (71.5%, vs. 69.1%).Furthermore, children whose mother (76.9%, vs. 68.9%for parttime, and 67.7% for unemployed or retired) or father (72.9%, vs. 71.2%for part-time, and 64.7% for unemployed or retired) was working full-time, and whose care givers reported doing no physical activity during weekdays (75.9%, vs. 66.3% for having done any physical activity) had a higher prevalence of physical inactivity during weekdays.Except for children with mothers whose educational level was primary school or below (59.4%), the educational level of parents (71.1-73.9%)did not have a significant impact on the prevalence of physical inactivity during weekdays.(Fig. 1).
In terms of physical inactivity during weekends, a higher prevalence was observed among children who were female (28.5%), delivered at 37-39 weeks of gestation (27.2%), thirdborns of the family (32.8%), had been hospitalised three times or more since birth (27.8%), spent more than 1 h/day on electronic games (27.7%), and whose mother (27.2%) or father (40.4%) had a part-time job, whose mother (34.5%) or father (29.6%) had primary school or below as the highest education level attained, and whose care givers did not do any physical activity during weekends (31.3%) (Fig. 2).

Discussion
In our study, it was found that a large proportion of children (71.4%) had less than an hour physical activity during weekdays.
Nearly three-fifths of the care givers had no physical activity during weekdays (58.0%) and weekends (56.7%).Children who were female, later-born in the family, hospitalised for at least three times since birth, and spent less than an hour on electronic games per day were more likely to be physical inactive during weekdays.The percentage of children who spent less than an hour on physical activity was lower during weekends (25.8%).
During weekends, a higher likelihood of physical inactivity was identified among children who were female, whose mothers were unemployed/retired, and whose care givers were physically inactive.However, there was no significant association between parents' educational level and child's physical inactivity after adjusting for confounders.
According to the World Health Organization, all forms of movement, whether for leisure, transportation or work, are considered physical exercise. 11Both vigorous and moderate physical activity are beneficial to health.The World Health Organization recommends that children aged between 3 and 17 should engage in at least 60 min of MVPA.However, we found that 71.4 and 25.8% of children had less than 1 h of physical activity during weekdays and weekends, respectively.This prevalence of physical activity was higher in Hong Kong compared to pre-school children in Shanghai, who spent an average of 168.0 total minutes of MVPA per day and met the standard of WHO. 14 In our study, we found that female children were less likely to engage in physical activity than males during both weekdays and weekends.One possible reason for this is parental support.Previous studies have shown that parents play a significant role in encouraging boys to be more physically active than girls, and the strongest relationship was observed when both parents played an equal role in assisting their child. 15The difference in parental support may influence the child's motivation to engage in physical activity.We have also found that children who have been hospitalised three times or more since birth are more likely to be physically inactive during weekdays.A similar outcome was reported in a previous study 16 which found that a shorter duration of physical activity was associated with hospital admission.Pfeiffer et al. suggested that child's physical activity level may be influenced by parents' perception of their child's athletic competence (r = 0.16, P ≤ 0.01), a newly identified factor in the study. 7hey argued that parents might provide or restrict physical activity opportunities for their children depending on their perception of their children's physical abilities.In the context of our study, parents may perceive children with a history of hospitalisation to be physically weaker, and may be less likely to encourage physical activity of their children.
There was a positive correlation between the levels of physical activity of children and their parents.Consistent with previous studies, physically inactive care givers were more likely to have physically inactive children. 15The amount of MVPA was used to measure the amount of daily physical level.Previous literature suggested that the MVPA level of both mothers and fathers positively affects the level of MVPA of their children.Furthermore, a strong relationship was found between sedentary behaviour and MVPA in obese parents and their children, with a stronger association showing at weekends (r = 0.253) than on weekdays (r = 0.177). 17Promoting increased MVPA and reducing sedentary time may help to improve children's health.Additionally, a study suggested that toddlers and pre-schoolers who engaged in higher levels of MVPA were significantly associated with better sleep outcomes. 18Moreover, we found that children with unemployed or retired mothers were significantly less likely to be physically inactive.Similar findings have been reported in other studies, in which longer work hours for mothers may lead to increased sedentary time of children.One study reported that children whose mothers work longer hours were 8% more likely to watch more than 2 h of TV per day and had an additional 0.74 h of Internet use per week. 19In contrast, unemployed or retired mothers have more time to engage in physical activity with their children, resulting in increased physical activity time for their children.
This study revealed a new finding that children who spent more than 1 h on electronic games per day were more likely to engage in physical activity.However, previous studies identified screen time as a risk factor for decreased physical activity levels for pre-school children. 5Typically, screen time is measured by combining television watching and electronic gaming time.It is possible that a significant proportion of screen time, which was used to assess sedentary behaviour, may actually be spent on 1156 light to moderate physical activity. 20For instance, a previous study found that 42.1% of children played activity-based electronic games, and they spent 19.9% of their gaming time on such games. 20The researchers recommended that future studies should distinguish between activity-based and non-activity-based electronic games and clarify the recommended amount of time children should spend on activity-based electronic games.In our study, the unexpected association between electronic game playing time and physical inactivity may be explained by the engagement of activity-based electronic games, which have been found to have light to moderate levels of energy expenditure. 21ur study revealed that birth order was a significant predictor of a child's physical inactivity.However, the relationship between birth order and physical activity order is unclear, due to the lack of studies investigating this association.One study found no significant difference between the motor ability of child and the order of birth (P = 0.514), 22 while another study reported that the later-born children performed better on physical tasks than firstborn children. 23The birth order effect may be due to parental motivation to minimise child's activity level and the simulationseeking behaviour of firstborn child, as discussed in a previous study. 24The authors hypothesised that parents with more children may have lower tolerances for high levels of activity from multiple children, in comparison to the same level of activity by a single child. 24Another explanation proposed by the authors is the simulation seeking of the firstborn children, who have fewer study highlights the importance of parental support and behaviour in determining a child's physical activity level, and we recommend that public health policy be implemented to promote family-based physical activities to increase the physical activity of young children.Further research should focus on exploring the effectiveness of the interventions targeting high-risk children.

Table 1
Participant characteristics